A blockade is an effort to cut off food, supplies, war material or communications from a particular area by force, either in part or totally. A blockade should not be confused with an embargo or sanctions, which are legal barriers to trade, and is distinct from a siege in that a blockade is usually directed at an entire country or region, rather than a fortress or city. Also, a blockade historically took place at sea, with the blockading power seeking to cut off all maritime transport from and to the blockaded country; although stopping all land transport to and from an area may also be considered a blockade.

Close patrol of a hostile port, in order to prevent naval forces from putting to sea, is also referred to as a blockade. When a coastal city or fortress was besieged from the landward side, the besiegers would often blockade the seaward side as well. In the twentieth century, blockades sometimes included stopping all air traffic within the blockaded area. Most recently, blockades have sometimes included cutting off electronic communications by jamming radio signals and severing undersea cables.

Act of war

A blockade is defined by the Encyclopedia Britannica as an "an act of war by which a belligerent prevents access to or departure from a defined part of the enemy’s coasts."[1]

Governing laws

Whether or not a blockade was seen as lawful depended on the national laws of the nations whose trade was influenced by the blockade. The Brazilian blockade of Río de la Plata in 1826, for instance, was considered lawful according to British law, but unlawful according to French and American law. The latter two countries announced they would actively defend their ships against Brazilian blockaders, while Britain was forced to steer for a peaceful solution between Brazil and Argentina.[2]

Blockades were first defined in international law at the Congress of Paris in 1856. One of the agreed rules was that a blockade had to be effective in order to be lawful. This banned so-called "paper" blockades — blockades that were declared to the blockaded nation, but were not actively enforced, allowing the blockading party to seize the cargo of neutral states trading with blockaded harbors.[3] At the Declaration of London in 1909 another attempt was made to further protect the rights of neutral traders.[4] The treaty was only ratified by a few nations, preventing any application of the agreements. Parts of it were, however, applied during blockades in World War I.

First: the value of the item being blockaded must warrant the need to blockade. For example, during the 1962 Cuban Missile Crisis, the items to be blockaded (or "quarantined", to use the more legally- and politically-neutral term selected by PresidentJohn F. Kennedy) were medium-range missiles, capable of delivering nuclear weaponry, bound for Cuba. The need for the blockade was high because of the value of the missiles as a military threat against the United States.

Second: the strength of the blockading force must be equal to or greater in strength than the opposition. The blockade is only successful if the 'thing' in question is prevented from reaching its receiver. Again, the Cuban blockade illustration shows that the United States put to sea a number of warships to inspect and blockade the waters around Cuba. This show of strength showed the United States Navy forces were much larger and stronger in the area than their Soviet Navy counterparts.

Third: in the case of land blockades, choosing suitable terrain. Knowing where the force will be travelling will help the blockader choose where to blockade: for example, forcing a garrison between a high mountain pass in order to bottleneck the opposing force.

Fourth: the willpower to maintain a blockade. The success of a blockade is based almost entirely on the will of the people who maintain it. The Cuban blockade is an example of maintaining willpower to block the missiles from reaching Cuba despite the risk of starting a worldwide nuclear war.

Blockade running

Blockade running is the practice of delivering cargo (food, for example) to a blockaded area. It has mainly been done by ships (called blockade runners) across ports under naval blockade. Blockade runners were typically the fastest ships available and often lightly armed and armored. However, in the modern age, it has also been done by aircraft, forming airbridges, such as over the Berlin blockade after World War II.

From LoveToKnow 1911

BLOCKADE (Fr. blocus, Ger.
Blokade), a term used in maritime warfare. Originally a
blockade by sea was probably nothing more than the equivalent in
maritime warfare of a blockade or siege on land in which the army investing the
blockaded or besieged place is in actual physical possession of a
zone through which it can prevent and forbid ingress and egress. An attempt to cross such a zone without
the consent of the investing army would be an act of hostility
against the besiegers. A maritime blockade, when it formed part of
a siege, would obviously also be a close blockade, being part of
the military cordon drawn
round the besieged place. Even from the first, however, differences
would begin to grow up in the conditions arising out of the
operations on land and on sea. Thus whereas conveying merchandise
across military lines would be a deliberate act of hostility
against the investing force, a neutral ship which had sailed in ignorance of the blockade
for the blockaded place might in good faith cross the blockade line
without committing a hostile act against the investing force. With
the development of recognition of neutral rights the involuntary
character of the breach would
be taken into account, and notice to neutral states and to
approaching vessels would come into use. With the employment in
warfare of larger vessels in the place of the more numerous small
ones of an earlier age, notice, moreover, would tend to take the
place of de facto investment, and at a time when
communication between governments was still slow and precarious, such notice
would sometimes be given as a possible measure of belligerent tactics before the blockade
could be actually carried out. Out of these circumstances grew up
the abuse of " paper blockades." The climax was reached in the "
Continental Blockade " decreed by Napoleon in 1806, which continued till it was
abolished by international agreement in 1812. This blockade forbade
all countries under French dominion or allied with France to have any communication
with Great Britain. Great
Britain replied in 1807 by a similar measure. The first nation to
protest against these fictitious blockades was the United
States. Already in 1800 John Marshall, secretary of
state, wrote to the American minister in Great Britain pointing
out objections which have since been universally admitted. In the
following interesting passage he said: " Ports not effectually
blockaded by a force capable of completely investing them have yet
been declared in a state of blockade.. .. If the effectiveness of
the blockade be dispensed with, then every port of the belligerent
powers may at all times be declared in that state, and the commerce
of neutrals be thereby subjected to universal capture. But if this
principle be strictly adhered to, the capacity to blockade will be
limited by the naval force of the belligerent, and, in consequence,
the mischief to neutral
commerce cannot be very extensive. It is, therefore, of the last
importance to neutrals that this principle be maintained
unimpaired. I observe that you have pressed this reasoning on the
British minister, who replies that an occasional absence of a fleet
from a blockaded port ought not to change the state of the place.
Whatever force this observation may be entitled to, where that
occasional absence has been produced by an accident, as a storm, which for a moment blows off a fleet and
forces it from its station, which station it immediately resumes, I
am persuaded that where a part of the fleet is applied, though only
for a time, to other objects or comes into port, the very principle
requiring an effective blockade, which is that the mischief can
only be coextensive with the naval force of the belligerent,
requires that during such temporary absence the commerce to the
neutrals to the place should be free." 1 1 John Marshall, secretary of state, to Rufus King, minister to
England, 10th of September
1800, Am. State Papers, Class I, For. Rel. II, No. 181, J. B.
Moore, Digest of International
Law, vii. 788.

Again in 1803 James Madison wrote to the then American
minister in London: " The law
of nations requires to constitute a blockade that there should be
the presence and position of a force rendering access to the
prohibited place manifestly difficult and dangerous." 1 In 1826 and
1827 Great Britain as well as the United States asserted that
blockades in order to be binding must be effective. This became
gradually the recognized view, and when in 1856 the powers
represented at the congress of Paris inserted in the declaration there adopted
that " blockades in order to be binding must be effective, that is
to say, maintained by a force sufficient really to prevent access
to the coast of an enemy," they were merely enunciating a rule
which neutral states had already become too powerful to allow
belligerents to disregard.

Blockade is universally admitted to be a belligerent right to
which under international law neutrals are obliged to submit. It is
now also universally admitted that the above-quoted rule of the Declaration of Paris forms part of
international law, independently of the declaration. Being,
however, exclusively a belligerent right, it cannot be exercised
except by a belligerent force. Even a de facto belligerent
has the right to institute a blockade binding on neutrals if it has
the means of making it effective, though the force opposed to it
may treat the de facto belligerent as rebels.

It is also admitted that, being exclusively a belligerent right,
it cannot be exercised in time of peace, but there has been some
inconsistency in practice (see Pacific Blockade) which will probably
lead governments, in order to
avoid protests of neutral powers against belligerent rights being
exercised in mere coercive proceedings, to exercise all the rights
of belligerents and carry on de facto war to entitle them
to use violence against neutral infringers. This was done in the
case of the blockade of Venezuela by Great Britain, Germany and Italy in 1902-1903.

The points upon which controversy still arises are as to what
constitutes an " effective " blockade and what a sufficient notice
of blockade to warrant the
penalties of violation, viz. confiscation of the ship and of the cargo unless the evidence
demonstrates the innocence of the cargo owners. A blockade to be
effective must be maintained by a sufficient force to prevent the
entrance of neutral vessels into the blockaded port or ports, and
it must be duly proclaimed. Subject to these principles being
complied with, " the question of the legitimacy and effectiveness of a blockade
is one of fact to be determined in each case upon the evidence
presented " (Thomas F. Bayard, American secretary of state, to
Messrs Kamer & Co., 19th of February 1889). The British manual
of naval prize law sums up the cases in which a blockade, validly
instituted, ceases to be effectively maintained, as follows: - (1)
If the blockading force abandons its position, unless the abandonment be merely
temporary or caused by stress of weather, or (2) if it be driven
away by the enemy, or (3) if it be negligent in its duties, or (4)
if it be partial in the execution of its duties towards one ship
rather than another, or towards the ships of one nation rather than
those of another. These cases, however, are based on decisions of
the British admiralty court and cannot be relied on absolutely as a
statement of international law.

As regards notice the following American instructions were given
to blockading officers in June 1898: " Neutral vessels are entitled
to notification of a blockade before they can be made prize for its
attempted violation. The character of this notification is not
material. It may be actual, as by a vessel of the blockading force,
or constructive, as by a proclamation of the government maintaining
the blockade, or by common notoriety. If a neutral vessel can
be shown to have had notice of the blockade in any way,
she is good prize, and should be sent in for adjudication; but
should formal notice not have been given, the rule of
constructive knowledge arising from notoriety should be
construed in a manner liberal to the neutral.

" Vessels appearing before a blockaded port, having sailed
without notification, are entitled to actual notice by a blockading
vessel.

They should be boarded by an officer, who should enter in the
ship's log the fact of such notice,
such entry to include the name of the blockading vessel giving
notice, the extent of the blockade, the date and place, verified by
his official signature.
The vessel is then to be set free; and should she again attempt to
enter the same or any other blockaded port as to which she has had
notice, she is good prize. Should it appear from a vessel's
clearance that she sailed after notice of blockade had been
communicated to the country of her port of departure, or after
the fact of blockade had, by a fair presumption, become commonly
known at that port, she should be sent in as a prize." The
passages in italics are not in accordance with the views held by
other states, which do not recognize the binding character of a
diplomatic notification or of constructive notice from
notoriety.

The subject was brought up at the second Hague Conference (1907). The Italian and Mexican delegations
submitted projects, but after a declaration by the British delegate
in charge of the subject (Sir E. Satow) that blockade not having
been included in the Russianprogramme, his
government had given him no instructions upon it, the subject, at
his suggestion, was dropped. A Vteu, however, was adopted
in favour of formulating rules on all branches of the laws and
customs of naval war, and a convention was agreed to for the
establishment of an international Prize Court (see Prize). Under Art. 7 of the latter convention the
Court was to apply the " rules of international law," and in their
absence the " general principles of justice and equity." As soon as possible after the close of
the second Hague Conference the British government took steps to
call a special conference of the maritime powers, which sat from
December 4, 1908 to February 26, 1909. Among the subjects dealt
with was Blockade, the rules relating to which are as follow: Art.
1. A blockade must not extend beyond the ports and coasts belonging
to or occupied by the enemy.

Art. 2. In accordance with the Declaration of Paris of 1856, a
blockade, in order to be binding, must be effective - that is to
say, it must be maintained by a force sufficient really to prevent
access to the enemy coastline.

Art. 3. The question whether a blockade is effective is a
question of fact.

Art. 4. A blockade is not regarded as raised if the blockading
force is temporarily withdrawn on account of stress of weather.
Art. 5. A blockade must be applied impartially to the ships of all
nations.

Art. 6. The commander of a blockading force may give permission
to a warship to enter, and subsequently to leave, a blockaded port.
Art. 7. In circumstances of distress, acknowledged by an officer of the
blockading force, a neutral vessel may enter a place under blockade
and subsequently leave it, provided that she has neither discharged
nor shipped any cargo there.

Art. 8. A blockade, in order to be binding, must be declared in
accordance with Article 9, and notified in accordance with Articles
I I and 16.

Art. 9. A declaration of blockade is made either by the
blockading power or by the naval authorities acting in its name. It
specifies (I) the date when the blockade begins; (2) the
geographical limits of the coastline under blockade; (3) the period
within which neutral vessels may come out.

Art. to. If the operations of the blockading power, or of the
naval authorities acting in its name, do not tally with the particulars, which, in accordance
with Article 9 (I) and (2), must be inserted in the declaration of
blockade, the declaration is void, and a new declaration is
necessary in order to make the blockade operative.

Art. 11. A declaration of blockade is notified: (I) to neutral
powers, by the blockading power by means of a communication
addressed to the governments direct, or to their representatives
accredited to it; (2) to the local authorities, by the officer
commanding the blockading force. The local authorities will, in
turn, inform the foreign consular officers at the port or on the
coastline under blockade as soon as possible.

Art. 12. The rules as to declaration and notification of
blockade apply to cases where the limits of a blockade are
extended, or where a blockade is re-established after having been
raised.

Art. 13. The voluntary raising of a blockade, as also any
restriction in the limits of a blockade, must be notified in the
manner prescribed by Article 11.

Art. In.. The liability of a neutral vessel to capture for
breach of blockade is contingent on her knowledge, actual or
presumptive, of the blockade.

Art. 15. Failing proof to the contrary, knowledge of the
blockade is presumed if the vessel left a neutral port subsequently
to the notification of the blockade to the power to which such port
belongs, provided that such notification was made in sufficient
time.

Iv. 3 a Art. 16. If a vessel approaching a blockaded port has no
knowledge, actual or presumptive, of the blockade, the notification
must be made to the vessel itself by an officer of one of the ships
of the blockading force. This notification should be entered in the
vessel's logbook, and must state the day and hour, and the
geographical position of the vessel at the time. If through the negligence of the officer
commanding the blockading force no declaration of blockade has been
notified to the local authorities, or if in the declaration, as
notified, no period has been mentioned within which neutral vessels
may come out, a neutral vessel coming out of the blockaded port
must be allowed to pass free.

Art. 17. Neutral vessels may not be captured for breach of
blockade except within the area of operations of the warships
detailed to render the blockade effective.

Art. 18. The blockading forces must not bar access to neutral ports or coasts.

Art. 19. Whatever may be the ulterior destination of a vessel or
of her cargo, she cannot be captured for breach of blockade, if, at
the moment, she is on her way to a non-blockaded port.

Art. 20. A vessel which has broken blockade outwards, or which
has attempted to break blockade inwards, is liable to capture so
long as she is pursued by a ship of the blockading force. If the
pursuit is abandoned, or if the blockade is raised, her capture can
no longer be effected.

Art. 21. A vessel found guilty of breach of blockade is liable
to condemnation. The cargo is also condemned, unless it is proved
that at the time of the shipment of the goods the shipper neither
knew nor could have known of the intention to break the blockade.
(T. BA.)

A blockade is any effort to make sure that supplies, troops, information or aid do not reach an opposing force. Blockades are used in nearly all militarycampaigns and the tool of choice for economic warfare on an opposing nation. The International Criminal Court plans to include blockades against coasts and ports in its list of acts of war in 2009.

Historical blockades

Historical blockades include:

The Spartan blockade of Athens following the Battle of Aegospotami, depriving Athens of the ability to import grain or communicate with its empire.

The Dutch Republic's blockade of the Scheldt between 1585 and 1792, denying Spanish-ruled Antwerp's access to international trade and shifting much of its trade to Amsterdam.

British blockade of France and its allies during the French Revolutionary War and Napoleonic War

Israeli sea and land blockade of the Gaza Strip since the outbreak of the Second Intifada (2000) and up to the present.

Israeli blockades of some or all the shores of Lebanon at various times during the Lebanese Civil War (1975–1990), the 1982 Lebanon War, and the 1982-2000 South Lebanon conflict - resumed during the 2006 Israel-Lebanon conflict.